“Soft drinks 'bigger gout risk than alcohol'” read the headline in The Daily Telegraph today. It reported that “drinking too many sugary soft drinks and fruit juices can substantially increase...

“Soft drinks 'bigger gout risk than alcohol'” read the headline in The Daily Telegraph today. It reported that “drinking too many sugary soft drinks and fruit juices can substantially increase the risk of gout”. Gout can be extremely painful and is caused by a build up of uric acid that crystallises in the joints. Uric acid is formed by the breakdown of purines which occur naturally in the body as well as in the diet. Traditionally, the advice is to avoid red meat and alcohol as they have high levels of purines and can make gout worse. However the Telegraph said “the risks associated with these drinks were higher than with certain types of alcohol”.

This story is based on a well-designed study in more than 46,000 men that found those who drank two or more cans of soft drinks a day increased their risk gout by 85 per cent compared with men who drank less than one soft drink a month. It provides yet another reason why drinking sugary fizzy drinks is not good for your health.

Where did the story come from?

Drs Hyon Choi and Gary Curhan from the Universities of British Columbia and Harvard carried out this research. The study was funded in part by the National Institutes of Health and TAP Pharmaceuticals. It was published in the peer-reviewed British Medical Journal.

What kind of scientific study was this?

This study was part of a large prospective cohort study looking at the health of male health professionals. This study recruited 51,529 men aged 40 to 75 in 1986 and the researchers selected the 46,393 men who did not have gout at the start of the study.

Upon enrolment, the men filled out standard questionnaires about their food and drink consumption, including their consumption of fizzy drinks and foods and drinks containing fructose, a type of sugar found in fizzy drinks, fruit, and products such as corn syrup. The men provided updated information about their food and drink consumption every four years.

Every two years, the men were sent a questionnaire, which asked whether they had been diagnosed with gout. A second questionnaire with detailed questions was posted to the men who reported a gout diagnosis. This allowed the researchers to confirm the diagnosis based on accepted criteria from the American College of Rheumatology, but not a blood test. The study lasted for 12 years.

The researchers then compared the risk of developing gout in men with different levels of average fizzy drink and fructose consumption over the 12-year period. They adjusted these analyses for factors which might affect results, such as the men’s consumption of alcohol, meat, seafood, vitamin C and vegetables rich in purine, their use of certain medicines (diuretics), body mass index, total amount of energy consumed, age, and the presence of high blood pressure or chronic kidney failure.

What were the results of the study?

About 1.5% of the men (755) developed gout during the study. Men who drank more fizzy drinks were more likely to develop gout than those who drank fewer fizzy drinks.

Men who had more than one fizzy drink a day increased their risk by 45%; two or more drinks a day increased the risk by 85%, compared with men who drank less than one fizzy drink a month. Diet fizzy drinks did not increase the risk of gout. People with the highest intake of fructose doubled their risk of gout compared with those with the lowest intake.

What interpretations did the researchers draw from these results?

The researchers concluded that consuming non-diet fizzy drinks and fructose increases the risk of developing gout. They say that the increase in risk seen with two or more soft drinks a day is slightly higher than that seen with alcoholic spirits.

What does the NHS Knowledge Service make of this study?

This was a well-designed and conducted study which has several strengths, including its large size, prospective design, its use of accepted criteria for the diagnosis of gout, and the use of repeated food questionnaires. Some points to consider when interpreting the study are that:

As with all cohort studies, there is the possibility that the results are affected by imbalances between the groups other than the one of interest (fizzy drink consumption). The authors did try to adjust for these, which increases confidence in the results, although the possibility that some other factor is playing a role cannot be ruled out completely.

This study only looked at men who were health professionals and mainly white, this may explain the relatively low overall risk of developing gout and implies that these results may differ in women or for other groups of men.

Although fructose is contained in fruit and fruit juices, the benefits of eating fruit are likely to far outweigh the risk of developing gout. Reducing fructose intake from non-fruit sources, such as fizzy drinks, is a better strategy for reducing risk of gout.

This study provides yet another reason why sugary, fizzy drinks are not good for your health.